Current digital broadcasting system adopts a copyright protection scheme, so-called “copy-once”, which does not permit copying a broadcast program recorded on a digital recording device to another digital recording device while leaving the original broadcast program. For the digital broadcasting, since quality and speed of copy are improved more than those of analogue broadcasting, unauthorized copies or so-called pirated copies of the broadcast program can be easily generated. The above copyright protection system is based on a viewpoint that a need exists for a stronger copyright protection structure. Currently, CPRM (Content Protection for Recordable Media) is employed as the copyright protection scheme which achieves the copy-once. A CPRM-compliant recording medium stores MKB (Media Key Block) and a media ID unique to the recording medium. The content is stored in the CPRM-compliant recording medium after being encrypted using MKB, a media key generated using a device key unique to the recording device, and a media ID. When the content is copied from the CPRM-compliant recording medium to another recording medium by a CPRM-noncompliant device, encrypted data themselves can be recorded, while MKB and the media ID cannot be copied. Accordingly, there is no MKB necessary to decrypt the encrypted data and thus the media key cannot be generated to reproduce the content in the another recording medium. Alternatively, the media key generated is different because of different MKB and, as a result, the encrypted data cannot be decrypted properly and the content cannot be reproduced, which precludes making a copy of the content.
In the existing terrestrial digital broadcasting, a program is broadcasted after a copy control signal indicating the copy-once is added thereto. Accordingly, in order to record (time-shift) the digital broadcast program, it is necessary to use a recording device and a recording medium that are CPRM-compliant. In addition, when the broadcast program of copy-once is recorded, the broadcast program cannot be copied to another (CPRM-noncompliant) digital device or recording medium as described above, and the content recorded on the recording medium can be reproduced only by CPRM-compliant reproduction device. In a copy-once system, when a user transfers the broadcast program content recorded by a recording device to the recording medium such as a DVD, the content is not “copied” but “moved” erasing the broadcast program (original data) stored in the recording device. If this movement of the content is failed, neither the original data nor the data in the recording medium can be used. Therefore, the existing copy-once system is inconvenient for legitimate purchasers of program content who have no intention of making an unauthorized copy, that is, for good users.
In order to deal with such a problem of the copy-once, there is a conventional art suggesting a technique which provides a digital broadcast program which “can be copied a certain number of times” instead of the “copy-once”, that is, the content can be copied up to the certain number of times. Patent Document 1, for example, suggests a method to provide a copy history table encrypted in an external recording medium or a memory in the information processing apparatus (recording device or copying device) for recording the content and update entry in the table in accordance with the number of copies of the content, which is permitted to be copied up to the certain number of times. In addition, Patent Document 2, for example, suggests to restrict the number of apparatus which can make a copy and the number of copies that can be made by recording a device ID, the number of apparatus which can make a copy and a maximum number of copies that can be made in a subsidiary recording section of the recording medium.
However, the existing CPRM-compliant device and CPRM-compliant recording medium are not provided with a format permitting an arbitrary number of copies to be made. Therefore, when the digital broadcast is received including copy control information that indicates “copying is permitted up to 3 times”, for example, and directly recorded in the CPRM-compliant recording medium (an SD memory card and the likes) instead of an internal memory of the recording device, the information that indicates “copying is permitted up to 3 times”, that is, a right to copy the content up to 3 times is lost. Since the copy apparatus disclosed in Patent Document 1 records the number of copies that can be made together with the content on the external recording medium or the memory, it solves the above problem to lose the information on the number of times. However, when the content recorded on a recording medium is moved to another recording medium using a device which does not recognize the format of the copy apparatus disclosed in Patent Document 1, the information on the number of copies that can be made is not recognized by the device and lost in the end. Although the copy apparatus disclosed in Patent Document 1 is capable of storing the content and the information on the number of copies that can be made in the memory of the copy apparatus, it is necessary to move the content to the external recording medium when the apparatus is replaced, which causes the same problem as described above. The information processing apparatus disclosed in Patent Document 2 has a similar problem that the content copied using a device which does not recognize the format of the information processing apparatus cannot be reproduced by the CPRM-compliant device.
In addition, if the arbitrary number of copies is permitted to be made, it may lead unauthorized copies or so-called pirated copies of the broadcast program by a person other than the legitimate user of the content, as mentioned at the beginning. Accordingly, there exists a need for the copyright protection system which prevents a right to copy from being passed to a third party other than the legitimate user of the content.
Patent Document 1: Japanese Patent Application Laid-Open No. 2001-351322
Patent Document 2: Japanese Patent Application Laid-Open No. 2005-190548